A wireless power transmission or a wireless energy transfer refers to a technology of wirelessly transferring electric energy to desired devices. In the 1800s, an electric motor or a transformer employing the principle of electromagnetic induction has been extensively used and then a method for transmitting electrical energy by irradiating electromagnetic waves, such as radio waves or lasers, has been suggested. Actually, electrical toothbrushes or electrical razors, which are frequently used in daily life, are charged based on the principle of electromagnetic induction. The electromagnetic induction refers to a phenomenon in which voltage is induced so that current flows when a magnetic field is varied around a conductor. Although the commercialization of the electromagnetic induction technology has been rapidly progressed around small-size devices, the power transmission distance thereof is short.
Until now, wireless energy transmission schemes comprise a remote telecommunication technology based on resonance and a short wave radio frequency in addition to the electromagnetic induction.
Among the above wireless power transmission technologies, an energy transfer technology based on magnetic resonance has been recently spotlighted.
In a wireless power transmitting system employing magnetic resonance, since an electrical signal generated between the transmitting side and the receiving side is wirelessly transferred through coils, a user may easily charge electronic appliances such as a portable device.